The present invention relates to fibers containing a corrosion inhibitor and the use to stabilize the raw concrete during cure and enhance physical properties of cured concrete, and to preserve and/or maintain integrity of steel reinforcements. More specifically, the invention relates to incorporating corrosion inhibitors into the fiber, with the inhibitors slowly evolving out of the fibers over extended periods of time. This produces an environment in the concrete that provides long-term protection while retarding and preventing corrosion of the steel rods and mesh utilized in concrete reinforcement. The incorporation of the inhibitor chemicals is accomplished by adding selected temperature stable and migratory inhibitors to a masterbatch suitable for producing monofilaments or extruding flat sheet material. The flat sheets can desirably be slit longitudinally and the fibers cut to the desired length.
The selected inhibitor molecules slowly evolve out of the fibers as the concrete ages and migrate through the porous channels of concrete to provide long term protection to the steel rods or mesh. These inhibitors possess the characteristic of being able to migrate through cured concrete from the fiber source to the surface of the metal. The treated fibers provide a new method of delivering long-term corrosion protection through migratory inhibitors designed to retard corrosion on the steel reinforcements including rods, cable, and mesh typically used in concrete reinforcement.
The present invention relates to a new method of providing long-term and delayed delivery of migratory corrosion inhibitors in a reinforced concrete structure to protect the steel used to reinforce. The present method of accomplishing this inhibition is to add inhibitors directly to the concrete mix such as described in U.S. Pat. Nos. 5,597,514 and 5,750,053 or to incorporate in a sealer as described in U.S. Pat. No. 6,174,461. The new process of incorporating the inhibitor molecules in a resin matrix in fibrous form can be utilized with either technique in new or raw concrete such as through the addition of the inhibitor impregnated fiber to an inhibitor containing sealer system as described in U.S. Pat. No. 6,174,461. This new method of using impregnated fibers as a source of migrating corrosion inhibitors provides an extended long-term availability of migratory corrosion inhibitor chemicals, the method complimenting the processes described in the above U.S. patents, all of which are assigned to the same assignee as the present invention. Since the impregnated fibers can be readily and conveniently utilized in combination with the concrete inhibitors disclosed in U.S. Pat. No. 6,174,461, it is preferable to employ both mechanisms.
Migratory corrosion inhibitors containing fibers can be prepared from a number of synthetic resin materials such as polyethylene, polypropylene, nylon, polyester, or mixtures thereof. The preferred fibers of the present invention are made from polypropylene which is the material selected in most installations. U.S. Pat. No. 6,054,512, assigned to the same assignee of the present invention describes the incorporation of corrosion inhibition chemicals in ABS resin while application Ser. No. 09/652,893, filed Aug. 31, 2000, entitled xe2x80x9cCORROSION INHIBITOR CONTAINERxe2x80x9d, also assigned to the assignee of the present invention describes the use of a polyvinyl alcohol resin as a delivery system for inhibitors. By way of further example, the formulation for the corrosion inhibitor of U.S. Pat. No. 6,054,512 comprises a blend of two or more members selected from dicyclohexylammonium nitrite, sodium nitrite, benzotriazole, sodium molybdate, sodium gluconate, and sodium sebacate, with such blends having been found to be compatible with the extrusion process, and mobile in concrete.
In accordance with the present invention, a selected migratory corrosion inhibitor preferably including a quantity of sodium sebacate is blended with a polyolefin such as polyethylene or polypropylene. The blend is then delivered to the inlet of a conventional vented extruder, with the barrel being heated to an appropriate temperature for the resin. Upon passing through the extruder, the extrudate is cooled and processed into a flat film form creating a sheet stock having a thickness of between about 5 and 25 mm. The sheet stock is then slit and chopped into fibers suitable for concrete reinforcement, with the reinforcement accordingly containing a source of a migratory corrosion inhibitor that provides corrosion protection to the steel reinforcements components over an extended period of time.
As an alternative, the blend may be extruded into a monofilament form chopped to an appropriate length such as from between about one-fourth inch to two inches in length. These filaments, when mixed with raw concrete, provide an effective source of migratory corrosion inhibiting chemicals especially useful in repair of concrete structures.
Therefore, it is a primary object of the present invention to provide an improved source of migratory corrosion inhibitor for protection of steel reinforcements used in concrete structures, wherein the corrosion inhibitor is blended in situ within the fiber, or otherwise compounded therewithin. While a variety of corrosion inhibitors may be utilized, the salts of dibasic acids containing from 8 to 12 carbon atoms and water soluble salts of oxycarbonic acids (glucoheptonates and gluconates), those comprising sodium sebacate, sodium gluconate, or mixtures thereof are preferred.
Other and further objects of the present invention will become apparent to those skilled in the art upon a study of the following specification and appended claims.